Lightning arrester



Sept. 13, 1927,

L. R. Go LAbAY ET AL LIGHTNING ARRESTER Filed Oct. 14, 1924 2 Sheets-sneer. l

Fir

/ ATTORNEY I, L. R. GOLLADAY ET AL LIGHTNING ARHESTER Filed Oct. 14, 1924 2 Sheets-Sheet 2 WITNESSES: INVENTORS Zia/rel? ca? 60/4906 1? TTORNEY Patented Sept. 13, 1927,

UNITED STATES LAWRENCE B. GOLLA DAY, OF EAST PITTSBURGH, AND IRVING SMITH, F PITTS- BURG H, PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC & MANUFAC- TUBI G COMPANY, a conPoRaTIoN or PENNSYLVANIA.

'LIGnT rNG ARR-ESTER.

Application as October 14, 1924'. .Serial No. 743,549.

' arrester disposed adjacent. to the transformer. The question as to whether it is desirable to leave the system unprotected or to employ a large number of lightning arresters disposed on the tops of the poles near the transformers is purely a matter of economy and depends upon the comparative cost of the interruptions in the continuity of the operation and in the exchange of the damagedtransformers and upon the cost of the lightning arresters themselves.

Modern lightning arresters of the distributionline type,.such as the autovalve arresters, for instance,.are so designed as to require practically no attention during many years of service under normal operating conditions. For practical reasons, the ar rester is usually inclosed ina strong porcelain casing to safeguard the same against .the influence of the weather and against accidental damage through rough handling,

and, in its'outer appearance, the arrester very closely resembles an insulator. In the course of service, it happens, however, that through abnormal operating conditions, such as in the case when a high-voltage line comes into contact with a low-voltage line, an-arrester may be damagedto such extent that it cannot clear the line upon the termination of the disturbance, and the distribution system to which the arrester is connected would thereupon continue to send currentthr'ough the arrester.

In some cases, especially in systems of large capacity, suflicient power will flow into the arrester to cause the same to break with a more or less explosive action. In many systems, however, there is not sufficient power to bring about the destruction of the arrester in a short time and the dangerous state of continuous arcing-in the interior of the arrester may continue for an unreasonably long time. By reason of its rugged construction, the arrester often remains externally intact, thus giving an appearance of perfect 1 operativeness, when, as a matter of fact, the apparatus to which the arrester is connected is without protection. Considerable trouble and expense is involved in locating the arresters that have failed.

The foregoing conditions make the cost of inspection and maintenance of a large number of scattered arresters out of proportion to the cost of their initial installation. A seriousobstacle is thus imposed on the maintenance of eflicient lightning-arrester protection in modern distribution systems.

; One object of our invention is to provide a distribution lightning arrester combining all the properties of rugged construction met with in modern lightning arresters, with means for securing a positive destruction of the arrester upon internal damage to the same. i

Another object of our invention is to provide a lightning arrester of the above-described character producing a visual indication upon failure of the same.

Still another object of our invention is to provide a protective device-of the above-described character that will quickly clear the line even under conditions where the power available for the destruction of the same is relatively small.

The foregoing and other objects of our invention will best b'eunderstood by reference to the accompanying drawing, wherein Figure 1 is a view in vertical section illustrating a lightning arrester embodying our invention,

Figs. 2, 3 and 4 are views similar to Fig.

1 illustrating modifications of our invention,

and

' Figs- 5 and ,6 are elevational views illustrating a lightning arrester embodying our invention as'mounted upon a pole, before and after failure of the arrester.

Referring to Fig. 1, a lightning arrester.

comprises a porcelain casing 1 resembling an insulator in external appearance. --The upper end of the casing constitutes a' cylindrical chamber 2 enclosing a plurality of resistor members 3 constituting a discharge path for abnormal surgeson the system to be protected. The arrester shown in the drawing 'is ofthe type known as the auto'i valve arrester, the principles of whichare 6 is' placed on the top of the disk column,

thereby providing a plurality ofminute gap devices assembled in a substantially vertical column. A series insulating. gap device the disks and an insulating gap device being held in place by means of a spring member '7 pressingthe same against a base mem her 8 which closes the bottom'of the chain-- her 2. A high-volta'gelead 11 vextends into the upper portion of the arrester and a groundl'ead 13 extends up through a cen-' trally' disposedopening in thebase 8 into the lower portion of the chamber. The

lcads are in electrical contact with terminalplates 14 and 15 at the upper'and the lower ends of the discharge path of the arrester.

The'top of the arrester is inclosed' by means of a porcelain cap 16 which is secured to the porcelain casing 1 by means of aninsulating gum poured into the space between the cap and the casing; The arrester is supcelain' casing.

The princ pal novel feature of our arported .by a clamp 17 surrounding thepor rester is a special construction of the por- I indication ofits failure.

'celain casing which renders the, same critical with respect to abnormal heating caused by. a continuous current "flowing through th'e arrester. According to our invention, abnormal heat generation in the arrester causes the-base portion 8 of the arrester and" the ground lead .13 to break ofi'- from the casing, therebystoppingthe discharge through the arrester and producing a visual In carrying out our invention,we make the base portion'8 0f the chamber 2 .of rela; ,tivelylow heat capacity as compared with the-remainder of the porcelain casing. "lhe base .member 8 is disposed in an interme:

' diate position between the upper, and' lower ends vof-the'casing' land it is joined withthe main body of. the casing lvby an integral tubular portion 21 of restricted cross section. The tubular portion 21' is so di's-" posed that the expansion of the base memher. '8,-.-attendant-upon heating the same,

brings the relatively weak tubular section 21 into bending or-shea'ring stress and causes the same to crack.

, "In operation,whe nthe, arrestei' is dame aged and fails to clear from tlie line, the' current passing through the arrester geners 3' are of disk shape and may "be separated by mica spacers 5,

crates heat. The heat isgenerated principally in the stack of resistor disks 3 and the heat flows along the path of best heat conduction toward-the base member 8, in-

creasing its temperature at a; time when the temperature of the main body of the casing 1 is. still relatively low on account of the i p'oor thermal connection between the disks '3 and/Che walls of the chamber 2. As-the 'base member 8 expands, the stress upon the 'weaktubular section- 21 increases until it breaks off. The base member ;-8 and the ground lead 13 drop out from the arrester under the action of their own weight and the weight of the members" constituting the discharge path in the arrester, augmented 'by the'action of the spring member 7.

By the utilization of the construction showninthe drawing, .it is possible to secure a ppsitive breakin theportion joining the base member 8 to the casing, with relatively slight energy input into the arrester without-materially a-fiecting the ruggedness a of the arresterstructure, since the weak portion of the casing which thus serv'es as a protective skirt of sufiicient mechanical strength to withstand theshocks and blows encountered ins'hipment and in rough handling during installation. v r In addition to the preferred'embodinient of our invention shown in Fig; 1, thesame' maybe afplfled in different modifications.

In Fig} 2, or instance, is shown a construc-.

porcelain casing 26 has its bottom 27 conthan the main, portion of the chamber. The

tion wherein the inner chamber 25 ofthe. v

'. nected to the side walls by a cylindrical ex tension 28 of somewhat smaller diameter diameter of the extension 28 is smaller than the discs 29in order to prevent the same.

fIOIllfalling out of the chamber 'when the bottom member 27 breaks-01f the casing upon abnormal heating. I

, H ,gl'n order to provide a contact between the bottom'terminal plate 31 ofthe ground lead 32 and the high-resistance disks 29, 9) filler 33,such 'as a metal disk, having good elec trical, and thermal, conductivity, is d is-' posed in the space between the thermal plate 31' and the high-resistance" dis'ksi The height channel- 33 i somewhat g ga r p hiilrthe height of the extension 28 in ord to bring the bottom member 27 and the termember disposed within the upper portion. of the 'arrester. v Such construction prevents the disksa'nd other loose members disposed within the chamber of the arrester from drop ing out of the same when'thg'abottom 1 mem n27 breaks off from the arrester. I In-Fig is shown a modification of the structure shown in'Fig. 1 wherein the tubular. seetion joining the-base member's to the 1. 'minal plate31 under" the action 0? the spring tubular section 21 and the base -member 8 9 I are protected by the overhanging bottom by a metallic plate 43, such as brass.

main body of the casing is avoided and the breakage of the base member is obtained by providing merely a restricted section at the joint of the base member and the main body of the casing 36. This Construction is less effective than the preferred arrangement shown in Fig. 1.

In Fig. 4 is shown a modification of our invention wherein the bottom of the chamber 41 of the porcelain casing 42 is inclosed The metallic plate inclosing the bottom of the casing may also constitute the lower terminal of the discharge path of the arrester. The bottom plate 43 is held at the edges by a thinwalled tubular extension 45 of the main body of the casing. The plate 43 is clamped tightly between the walls of the extension or maybe joined thereto by cement, for instance.

Upon abnormal operation of the arrester,

- the heat generated initially raises the temperature of the bottom plate 43 and the expansion of the bottom plate breaks the extension 45 off from the body of the casing 42. The broken off portion ofthe casing, together with the bottom plate '43, drops down, interrupting the circuit of the arrester,

and producing a visual sign of its failure.

The mounting ofour improved arrester is shown in Figs. 5 and 6( The arrester issecured to a cross arm mounted upon a pole carrying the line conductors and the distribution transformer.

line and the ground lead 13 is connected to the ground.

Fig. 6 shows the arrester after failure with the bottom of the arrester chamber hanging downward upon the ground lead 13. The fact that the ground lead drops off from the arrester and hangs down prevents any accidental damage that might occur in .case thehigh potential lead should fall off from the arrester. 7

Our invention is susceptible of various modifications not shown in the drawing and we desire that the language of the appended claims shall cover all such modifications.

e claim as our invention:

1. A double-walled casing comprising an The high-potential lead 11 of the arrester isconnected to the v as a result of abnormal heating. F

2. The combination with a device which may, at times, become overheated, of a casing therefor having a substantially cylindriplying a breaking stress in a radial direction closure portion a djacentto said cylindrical wall portion being in good thermal connection with the source of heat in said device, whereby said end closure portion may be readily heated to break said cylindrical wall portion by laterally applied stresses, the remainin portions of said casing being in relative y poor thermal connection with the source of heat in said device whereby they are not subjected to any substantial stresses resulting from unequal heating.

3. A lightning arrester comprising a' double-walled insulating casing having an outer wall portion having suflicient mechanical strength to withstand shocks incident to shipment-and handling, and having an interior bore, an inner. cylindrical wall member of reduced thickness joined at its lnner end to an intermediate portion of the interior bore of said outer wall portion, said inner cylindrical wall member being capable of withstanding relatively great steady pressures applied in an axial directionbut being easily subject to fracture as a result of radially applied pressures, and an vend wall port on joined to the'free end of said inner cylindrical wall member and capable of app ying a breaking stress in a radial direction as a result 'of abnormal heating, a

column of active lightning-arrestermaterial disposed within said casing in good thermal connection to said end wall portion, a flexible ground.lead connected at the end' of said column which rests on said end wall portion, and a high-potential lead entering the casing adjacent to the other end thereof..

- 4. The" combination with a columnar shaped lightning-arrester device, of a cas-- 1 ing therefor having a! substantially cylindrical bore and end closure portions, the

jacent' to one and closure portion having;

relatively great strength in an axial direc-., tion but being easily subjectto'fracture as a result of radially applied pressures, the.

end-closureportion. adjacent to said cylindrical wall portion being in good" thermal connection with the source of heat .in said device whereby said end" closure portion may be readily heated to break said. cylindrical wall portion by laterally applied casing having a cylindricalwall portion adstresses, the remaining portions of. said casf ing .beingin relatively poor thermal con-- *nection with the source of heat in said def 35 diameter than saidcolumn, an

vice whereby way are not subjected to any substantial stresses resulting from. unequal heating.

'5. A lightning arrester comprising a.

5, double-walled insulating casin having an outer substantially cylindrical? portion of suflicient mechanical strength to withstand shocks incidentto shipment and handling, an inner. cylindrical wall member of redueed thickness joined at its inner end to an ntermediate portion of the interior bore" of saidouter cylindrical portion, said inner 'cylindrical wall member being capable of radial direction as a result of abnormalheating, a column of active ].ightning-arraster material disposed within said casing n good thermal'connection to said end wall -25 portion, said end wall portion having a central o nin therein, 1a flexible ground lead exten ing trough said opening,'a terminal plate engaged to said ground lead and. disposed between said end wall and said col- 3o umn, springtensionmeans at the-other end I of sa1d column and" operative to expel said.

terminal plate and ground lead 'uponthe fracture of said inner cylindrical wall'member, :saidterm-inal plate 'havin -a smaller providgd within the internal bore of said a shoulder casing and operative after the expulsion of the terminal plate to prevent the expulsion of said column. from the casing. V

6. A lightning arrester comprising a vertically disposed cylindricalcasing of insu- '.la;ting material, a high-potential lead entering the upper portion of said casing, a

column of active material disposed within said easing, a flexible ground lead suspended from the bottom of the ar'rester, and means disposed underneath said column and operating upon the occurrence of abnormal heat-.

ing said column within said casing, the upper portions of said casing remaining intact.

7.- A lightning arrester comprising a ver tically disposed cylindrical casing of insulatini material, a high-potential lead entering t 6 upper portion of said casing, a colmg of said column to permit said ground lead to fall clear of the 'arrester while retain-- Q0 umn of active material disposed within said casing, a flexible =ground lead suspended from the bottom of the arrester, spring ten- 7 sion means pressing downwardly ;against the top of vsaid column, means operating upon the occurrence of abnormal heating of said column to permit said ground'lead to be. expelled from the casing, and means operative after the expulsion of the ground lead to prevent the expulsion ofv said column from said casing.

In testimonywhereof, we have hereunto I subscribed; our namesthis 10th day of October,1-924. I LAWRENCE R. GQLLADAY.

- rav nes. SMITH. a 

